Stay bolt for steam boilers



A. F. PITKIN.

STAY BOLT FOR STEAM BOILERS.

APPLICATION FILED OCT; 22. I92l.

Pamnted Oct. 17, 11922,

Fatented @ch 17, 12322,

sateen r. raw in, or scnaneernnrz, new

STAY BQLT IEQZZ-t STEAM Application filed @ctober 22, 1321. serial He. 509,551..

upon, the inner and outer sheets of steam boiler fireboxes, of the class or type known as flexible, in which, by reason of an articulation being provided between different members of the stay bolt structure, such flexibility is imparted to the structure as will substantially exempt it, and the connected firebox sheets. from bending strain under variations of temperature in the operation of the boiler.

The object of my invention is to provide a stay bolt structure of the type above specified which shall be of inexpensive construction; capable of universal flexibility, relatively to both the inner and outer firebox sheets; capable of indicating breakage, if occurring, and which will minimize liability to leakage by reduction of strain on the connections to the firebox sheets.

The improvement claimed is hereinafter fully set forth.

In the accompanying drawing: Figure 1 is a view, partly in side elevation,'and partly in axial section, of a stay bolt structure, illustrating an embodiment of my invention; and, Figs. 2 and 3, transverse sections, on the lines 1-'1 and 11-11, respectively, of Fi 1.

Tn the practice of my invention, the stay bolt proper comprises a solid cylindrical body, 1. and sockets 1* and 1", which are forged or upset on the opposite ends of the body. It is articulated to the outer sheet, A, of the firebox, by a plug, 2, which is fitted closely in an opening of corresponding form in the sheet, and is secured therein either by being welded thereto or screwed thereinto, in the ordinary manner. A short neck, 2 is formed centrally on the plug, 2, anda ball, 2*, which is in the form of a truncated sphere, of proper diameter to fit freely in the socket, 1, of the stay bolt, is forged or upset on the end of the neck further from the plug. A tell tale hole, 2, is drilled centrally in the plug and neck, extending from the outer side of the plug, nearly to, or

slightly into, the ball 2. The stay bolt proper 1s articulated to the inner sheet, f, or the firebox, by a plug bolt, 3, which is peripherally threaded to engage an internal thread on the sheet and has a squared outer end wrench seat, 3 and a ball, 3", which is formed on its inner end, and is of form similar to the ball, 2*, and of proper di= ameter to-fit freely in the socket, 1, of the bolt, 1. A tell tale hole, 3, is drilled in the plug bolt, 3, extending from its outer end nearly to, or slightly into, the ball, 3". it should be noted that the minimum diameter of the plug, 2, and of'the hole in the boiler sheet, A. in which it fits, must be slightly greater than the outside diameter of the sockets, 1 and 1, of the stay bolt proper.

As clearly shown in Fig. 1, so much of the internal surfaces of the sockets, 1 and 1", of the sta bolt proper, 1, as constitutes the bearing aces oi the sockets, is, in each socket, of truly truncated spherical form, and of diameter adapted to fit around one of the balls, 2 and 3, and extends between parallel transverse planes of the socket, at

right angles to the axial line of the bolt, and located at the inner end of the cylindrical opening in the socket and at the centre of the spherical bearing surface, respectively.

The remaining portions of the internal surfaces of the sockets are enlarged, as by being made of greater radius than that of the bearing surfaces, thereby providing free spaces, 1, 1, around the balls, 2 and 3 and between them and the surfaces of the sockets, throughout the internal surfaces of the latter, between planes at right angles to the axial line of the bolt, at the centres of the sockets and the bottoms of the chambers therein. The function of the formation of the sockets with hearing faces on their inner surfaces, between their centres and their bottoms, and free spaces 1, 1, on the outer sides of the planes of their centres, as above described, is to permit a limited degree of inward longitudinal movement of either or both of the plugs, 2 and .3, when secured in the boiler sheets, relatively tothe stay bolt proper, and preventing outward movement of the lugs and sheets. It will be seen that the re ief of compressive strain, which, under certain conditions, has been found to be exerted on stay bolts, will be efi'ectually accomplished. i

1n assembling the structure, the balls, 2

Q mes es and 3", of the plugs, 2 and 3, are inserted, respectively, in the sockets, 1 and 1", of the stay bolt proper, and the sockets are swaged over the balls, so as to grip them, but with sufiicient looseness to allow relative motion.

The assembled structure is inserted and secured in position in the firebox sheets, by.

' 3 of the bolt, 3, is then gripped with a wrench applied from the inside of the firebox and the plug, 3, is screwed up until the plug, 2, is drawn into place, in which it is secured b welding to, or screwing into, the sheet. T e plug, 3', is then further screwed up until the bolt is drawn to the proper tension, after which the wrench seat, 3, is cut off, and the end of the bolt turned over or expanded to make a tight joint with the sheet, in the ordinary manner.

I claim as my invention and desire to secure by Letters Patent:

1. In a three part stay bolt structure, the combination of a stay bolt, having a solid cylindrical body, and integral end sockets in which are formed bearing faces, adjacent to their outer ends, which faces are sections of spherical surfaces, said sockets being of greater depth between their centres and their bottoms than the radii of the bearing faces; and balls, bearing on the bearing faces of said sockets, and adapted to be se-' cured in the outer and the inner sheets, re-

spectively, of a steam boiler firebox.

2. in a jthree part stay bolt structure, the combination of a plug, adapted to be secured in the outer sheet of a steam boiler firebox,

and having a ball projecting from its inner end; a plug, threaded to engage the inner sheet ofa steam boiler firebox, and having a ballprojectlng from its inner end; and an interposed bolt, having a solid cylindrical body, and articulated to 'said balls by end sockets formed within it, said sockets having internal bearing faces for the balls between their centres and their outer ends, and being of such depth as provides free spaces around the balls. between the centres and the bottoms of the sockets.

3. In a three partstay bolt structure, the combination of a plug, adapted to be secured in the outer sheet of a steam boiler firebox,

and having a ball projecting from its inner end and a tell tale hole open at its outer end; a plug, threaded to engage the inner sheet of a steam boiler firebox, and having a ball projecting from its inner end, and a tell tale hole open at its outer end; and an interposed bolt, having a solid cylindrical body, and articulated to the balls of the plugs by end sockets, in which are formed internal bearing faces for the balls, adjacent to their outer ends, and being ofsuch depth as provides free spaces around the balls, between the centres and the bottoms of the sockets.

ARTHURv F. PITKIN.

Witnesses: RALPH P. L PoR'rE, P. A. LEONARD, 

